The book of Ecclesiastes can be easily misunderstood. If we put it in context with the rest of God's Word, and have an understanding as to who God is, it all becomes clear.   

Solomon gives us a glimpse into what life is like when we choose to ignore God and try to live on our own. The original sin in the garden was when Satan convinced Adam and Eve they didn't need God, but rather that they could be like God. Ever since, man has been trying to fulfill their life with everything but the hope and love of our Creator. Without an eternal perspective, it's all vanity.